Heat exchange unit



Dec. 23, 1941. R. M. STIKELEATHER HEAT EXCHANGE UNIT Filed Feb. 15, 1939 i 11 5! vi-P 7 4 i ||l i 1. i am I ings protect the extended high brazing temperatures.

Patented Dec. 23, 1941 HEAT EXCHANGE UNIT Robert M. Stikeleather, Dedham,

to B. F. Sturtevant Company,

Mass, assignor Boston, Mass.

Application February 15, 1939, Serial No. 256,475

5 Claims.

This invention relates to heat exchange tubes and relates more particularly to methods and apparatus for anchoring heat exchange tubes in end plates extending transversely of the tubes.

For the conditioning of air it is convenient to provide heat exchange tubes such, for example, as refrigerant condensers and air cooling refrigerant evaporators in units including several horizontal rows of tubes,.each row containingseveral tubes. The tubes are usually connected in a series-parallel circuit with respect to interior fluid flow, by return bends at the ends of adjacent' tubes. It is also usual to provide vertically extending end plates at the ends ofthe tubes, the end plates containing circular openings through which the tubes extend, with the end plates between the ends of the tubes and the return bends. The end plates serve as air guiding passages and to support and align .the tubes.

Heretofore it has been the practice to either solder or braze the end plates directly to the tubes. Neither practice has proved satisfactory. For duties such as for railroad cars where considerable motion and vibration is present, the end plates move relative the tubes and loosen the soldered joints. To braze the end plates to the tubes requires that the end plate and tubes be raised to the brazing temperature. Such high temperatures result in the relatively thin fins adjacent the end walls, always used on this type of tube, being burned and weakened.

According to this invention tubular bushings are expanded into the circular openings in the its position is regulated by the shoulders ll conend walls and the outer ends of the bushings are brazed to the ends of the tubes while simultaneously the. ends of the tubes are brazed to the return bends. The end walls and the bushsurface fins from the An object of the invention is to improve the method of securing end plates to heat exchange tubes.

Another object of the invention i to anchor end plates more securely to heat exchange tubes without damaging the tubes.

Other objects of the invention will be apparent from the drawing and the following description.

The invention will now be described with reference to the drawing, of which:

Fig. l is a side elevation in section of a heat exchange tube assembly embodying the invention, and

Fig. 2 is a sectional view along the lines 22 of Fig. 1.

Each end plate 5 is first provided with circular apertures at 6, each aperture being'substantially greater in diameter'than the copper tube 1 it is to receive. The plates 5 arethen tinned in the circular apertures with solder. Tubular copper bushings 8 have portions adapted to fit into the apertures 6 correspondingly tinned and the bushings are then placed within the apertures and are expanded into the end plate'by a suitable tool to take the shape chosen by Fig. 1 of the drawing. The expanded bushings have recessed portions 9 which fit into the circular apertures 6 and have the raised shoulder portions l0 and H on each side of each recessed portion 9.

The plate 5 is then placed on the tubes and tacting at their inner edges the outer edges of the innermost fins I2 which thus space properly the position of the tube ends with respect to the outer ends of the bushings 8. The outer ends I3 of the tubes are then flared as illustrated by Fig. 1 with the outer ends of the bushings 8 so a to tightly contact same. The return bend l4 is then placed in position as shown by Fig, 1

with its two ends within the flared portions I3 of the tubes.

After the above described assembly operations have taken place, heat is applied to the outer portions of the bushings 8 and the flared port ons M of the tubes, brazing compound is flowed in between the bushings 8 and the flared portions I3 of the tubes and between the ends of the return bend and the flared portions l3, and the bushings are brazed to the flared portions. of the tubes and the flared portions of the tubes are brazed to the ends of the return bend. .Sufiicient heat is also transmitted through the bushings 8 to cause their tinned portions to become sweated to the correspondingly tinned apertured interiors of the walls 5.

The end wall 5 protects the fins I 2 from the brazing heat. It is to be observed further that the end wall is not attached directly to the tubes as in the past but is attached to expanded bushings which are spaced from the tubes where attached to the end wa1ls,'thus providing flexibility and a more rugged assembly.

While one embodiment of the invention has been described for the purpose of illustration,

itshould be understood that the invention is notlimited to the exact apparatus and arrangevention.

What is claimed is:

1. A heat exchange tube assembly for air conditioning comprising a finned tube, a flexible bushing attached at its outer end to said tube but spaced from said tube throughout its inner portion, and an apertured end plate around and attached to said inner portion of said bushing at a point substantially spaced from the point of attachment of said bushing to said tube whereby said tube is flexibly supported through said bushing from said end plate, said inner end of saidbushing having a slot portion in an aperture of said plate and having raised shoulder portions on each side thereof, said plate being attached to said bushing by the contact of the outer surface of said slot portion with the plate surface around the aperture and by the contact of said shoulder portions with the side walls of said plate.

2. A heat exchange tube-assembly for air conditioning comprising ..a finned tube having a flared end portion, a flexible bushing attached bushings having slot portions in apertures in said plate and having raised shoulder portions on the sides thereof, said plate being attached to said bushings by the contact of the outer surfaces of said slot portions with the plate surface around said apertures and by the contact of said shoulder portions with the side walls of said plate.

4. A heat exchange tube assembly for air conditioning comprising a tube having spaced exat its outer end to said flared portion and havthe contact of-said shoulder portions with the side walls of said plate.

3. A heat exchange tube assembly for air conditioning comprising a pair of flnned tubes having flared end portions, a pair of flexible bushings having their outer ends attached to said flared portions and having their inner portions spaced from their respective tubes, an apertured end plate around and attached to said inner portion of said bushings, and a return bend having its ends within and attached'to said flared portions of said tubes, said tubes and said return bend being flexibly supported through said bushings from said end plate, said inner ends of said tended surface fins thereon, a flexible bushing attached at its outer end to the outer end of said tube but spaced from said tube throughout its inner portion, and an apertured end plate around and attached to said inner portion of said bushing, said bushing having a portion extending through said plate and contacting the outermost of said fins and serving to Position the outer end of said bushing relative the outer end of said tube, said tube being flexibly supported through said bushing from said end plate. said inner end of said bushing having a slot portion in an aperture of said plate and having raised shoulder portions on each side thereof, said plate being attached to said bushing by the contact of the outer surface of said slot portion with the plate surface around the aperture and by the contact of'said shoulder portions with the side walls of said plate.

5. A heat exchange tube assembly for air conditioning comprising an apertured plate, a pair of flnned tubes having flared end portions extending through apertures in said plate, a return bend having its ends within and attached to said flared portions, and a pair of flexible bushings each attached at its inner end'to said plate at one of said apertures and having its other end around and'attached to one of said flared portions, said tubes and said return bend being flexibly supported through said bushings from said end plate, said inner ends of said bushings having slot portions in apertures in said plate and having raised shoulder portions on the sides thereof, said plate being attached to said bushings by the contact of the outer surfaces of said slot portions with the plate surface around said apertures and by the contact of said shoulder portions with the side walls of said plate.

ROBERT M. STIKELEATHER. 

